I am running Roon Server under Ubuntu 22.04 on a custom-built PC with 16 GB RAM. Since updating to Build 1148, I’ve noticed never-before seen peaks of RAM usage, up to 11 GB while eternally creating search indexes on the server. My library is nearing 245k tracks, so if the behavior on your machine is similar, 16 GB RAM with 608k tracks will never be enough.
I’ll add that previous to this last update, my Roon Server was comfortably and stably running with RAM usage between 5-6 GB and the odd peak at 7,5-8 GB. The new release has made RAM usage increase sharply.